Actuators provided with a motor and a strain wave gearing as a reduction mechanism are well-known. There are numerous control systems for actuators having this configuration to which is applied a semi-closed control system for performing control using only information concerning a motor shaft, and not using information concerning a load shaft, which is the output shaft of the strain wave gearing. In this case, angular transmission errors in the strain wave gearing that include hysteresis properties impede the performance of high-velocity and high-accuracy positioning control. The present inventors have therefore proposed methods for compensating for angular transmission errors using a model that has been analyzed, modeled, and constructed for angular transmission error (Patent Documents 1 to 4).
However, in an actuator in which a strain wave gearing is used as a reduction mechanism, a full-closed control system for controlling the position of a load shaft using both motor shaft information and load shaft information is also well-known. The present inventors have proposed a method for preventing degradation in positioning control performance of the load shaft caused by nonlinear characteristics of the strain wave gearing in such a control device (Patent Document 5).